1. Field of the Invention
The present invention pertains to the art of electrical switches and, more particularly, to a switch assembly which utilizes a push button to deflect a spring to unite a mobile contact with a stationary contact.
2. Discussion of the Prior Art
It is well known in the art to provide a push button actuator for an electric or electronic switch. More specifically, it is known to utilize a plunger or push button within a housing to bias a spring member which, when pressure is applied to the push button, brings various contacts into electrical communication. Many of the recent designs represent attempts to eliminate either the number of moving parts, the number of total parts, the assembly time or assembly costs.
In a common design, a push button, which extends outside of a housing, is located over a curved spring. Two contacts are located beneath the spring, and when the spring is depressed via the push button, the two contacts are brought into electrical communication. For example, U.S. Pat. No. 5,055,642, issued to Miyata, describes a push button switch in which two electrical contacts are fixed in a location beneath a concave spring or diaphragm. Three contacts are disposed on a base inside the housing, below the diaphragm, with two laterally disposed and one at the center. With the push button in a default position, the diaphragm is maintained in a concave condition, with each of its two ends in contact with a respective, laterally disposed contact. When pressure is applied to the push button, the diaphragm is deformed, from its concave shape, so as to bring the centrally located contact into electrical communication, across the diaphragm itself, with the laterally spaced contacts. The result is a snap-action push button switch which operates via a deformable diaphragm. This design works well, but maintains a number of flaws. First, the movement of the diaphragm from the concave position to a position in which it may abut both the lateral and central contacts puts substantial strain on the diaphragm itself. In addition, in such a design, each contact represents a fixed piece in the housing and is not designed to be removed for repair or replacement.
U.S. Pat. No. 4,789,764, issued to Doros, describes an attempt to overcome these problems. In that design, a concave-convex spring element is disposed within a housing with a fixed contact disposed not on the base of the housing, but above the spring and laterally of a centralized push button. Because this spring element does not extend outside of the housing, a fixed end of the spring element functions as an electrical lead to which a wire may be connected. Due to the contorted shape of this spring element and the design of the housing, a non-fixed end of the spring is forced into electrical communication with the fixed electrical contact. As in U.S. Pat. No. 5,055,642, actuation of the push button causes extreme deformation of the spring element in order to bring the contacts into electrical communication. Although these two designs contain only a few moving parts, the parts that do move, i.e. the spring element, diaphragm, and push button, move a relatively great distance, as compared to the total structure. The existence and extent of these moving parts is considered to present a number of stress points making the overall design prone to failure.
Switch assemblies, generally constructed in the manner set forth above, can be used in various environments. One particular environment of concern is in appliances, particularly clothes washing and drying machines. In such appliances, it is common to provide a control panel having various buttons which are associated with switches for enabling a consumer to select various operating parameters of the machine for a particular cycle. For instance, in the case of washing machines, it is common to provide a row of buttons which enable the consumer to select a desired water temperature for both washing and rinsing cycles. It would not be uncommon to provide a bank of buttons in a single housing, with the buttons being associated with switches and further being interconnected such that the depression of one button would automatically cause the release of another button. For example, if the bank of buttons or switches control the selection between hot/hot, warm/warm, warm/cold and cold/cold wash/rinse temperatures respectively, the depression of the button associated with the warm/warm setting would automatically cause any other depressed button in the bank to be released. In general, cams and levers are utilized to interconnect the various push buttons to operate in this manner. In any event, since the useful life of such an appliance can be quite long, the switches must be extremely reliable. However, the overall construction of the switch assembly directly affects its associated cost reflected in both the components themselves and the time needed for assembly and installation. In general, it is considered that the installation of conventional multi-switch devices are often difficult or time consuming. Primarily, the time and expense comes from being forced to install individual wires to at least two different locations for each switch in a known multi-switch device. In any event, there exists a need in the art for a push button switch assembly which overcomes the drawbacks of the prior art and which represents an overall switch which is easy to assemble, is cost effective and requires a minimum number of components, while being extremely reliable over a prolonged period of time.
The present invention is directed to a switch assembly which utilizes a small number of parts, is easy to assemble and functions in a reliable manner. In general, a switch assembly constructed in accordance with the present invention includes a center spring which carries a first contact and which is adapted to shift upon depression of a push button in order to abut a second contact which is mounted in a stationary position relative to an overall housing. In the most preferred embodiment, the second contact is placed in proximity to an apex of the spring, opposite the push button. When the push button is depressed, the spring shifts from a convex condition to a concave condition wherein the first and second contacts are engaged to complete an electrical circuit. Therefore, one embodiment utilizes an overcenter spring that can be selectively maintained in either an activating or a deactivating position.
In the most preferred form of the invention, the spring is held in place by the interaction of ends of the spring with portions of the housing. That is, the housing is specifically designed with a notch or groove therein into which at least one end of the spring is seated, while the other end of the spring is adapted to abut an opposing side of the housing. When pressure is applied to the center of the spring through the push button, the spring is caused to bend due to the engagement between the housing and each end portion of the spring. When the push button is completely depressed, the spring reaches its maximum deflection wherein the contacts are engaged. One end of the spring projects from the housing to readily enable a first wire to be attached to the switch assembly, and the housing is formed with an opening which enables another wire to be directly connected to the stationary contact. Therefore, in accordance with this embodiment, the switch assembly generally includes a housing, defined by a lower body portion and a cover, at least one stationary contact, the spring and the push button. The stationary contact, spring and push button are adapted to be pre-assembled within the lower housing portion and the cover is preferably snap-fittingly mounted thereon. In a second embodiment of the invention, the housing is formed of a one-piece unit with a living hinge interconnecting the body portion and the cover. In accordance with this embodiment, the second contact is preferably mounted to the cover in a position which aligns with the first contact carried by the spring when the cover is closed. Most preferably, the cover includes side leg portions which extend into the body portion of the housing and abut sections of the spring to retain the spring sections in desired grooves or detent portions of the housing body.
In accordance with the invention, multiple switches can be maintained in a single housing or a dedicated housing can be utilized for each switch. In addition, the switch assembly of the present invention can be readily designed to be an ON/OFF type switch as set forth in accordance with the first embodiment of the invention or as a momentary contact switch wherein only a relatively slight deflection of the spring is required to engage the first and second contacts. In any event, the switch assembly of the present invention requires only a minimum number of parts that can be easily assembled to establish an effective and reliable electrical switching system. When multiple switches are utilized in connection with a single housing, it is desired in accordance with the present invention to bundle various wires of the switch assembly in a harness block. Although the switch assembly of the present invention can be employed in a variety of environments, the switch assembly is seen to have particular applicability for use in the field of appliances.
Additional objects, features and advantages of the invention will become more readily apparent from the following detailed description of preferred embodiments thereof, when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views.